diff --git a/extension/manifest.json b/extension/manifest.json
index 4d165e7..9f9097a 100644
--- a/extension/manifest.json
+++ b/extension/manifest.json
@@ -30,5 +30,12 @@
     "nativeMessaging"
   ],
 
-  "host_permissions": ["<all_urls>"]
+  "host_permissions": ["<all_urls>"],
+
+  "commands": {
+    "velox-grab-current-tab": {
+      "suggested_key": { "default": "Ctrl+Shift+U" },
+      "description": "Send the current tab's URL to Velox"
+    }
+  }
 }
diff --git a/extension/src/background/capture/downloads-api.ts b/extension/src/background/capture/downloads-api.ts
new file mode 100644
index 0000000..68a8fc6
--- /dev/null
+++ b/extension/src/background/capture/downloads-api.ts
@@ -0,0 +1,186 @@
+// The downloads.onCreated safety net.
+//
+// Some downloads never reach the blocking header hook — a form POST's result, a
+// service-worker-generated response, a click that Firefox routed straight to its own
+// downloader. Those surface here. If one looks like something the daemon should own,
+// offer it FIRST and only then cancel + erase Firefox's copy — so a failed or slow offer
+// can never leave the user with no download at all.
+//
+// blob:/data: downloads are left to Firefox: their bytes exist only in the page, and the
+// daemon cannot fetch a blob URL.
+
+import type { CaptureOfferParams, CaptureOfferResult, CaptureRules, Cookie } from '../../shared/protocol/index.js';
+
+import { guessFilename, toWireCookies, type CookieRecord } from './index.js';
+import { filenameExtension, hostExcluded } from './rules.js';
+
+export interface DownloadItem {
+  id: number;
+  url: string;
+  finalUrl?: string;
+  referrer?: string;
+  filename?: string;
+  mime?: string;
+  /** -1 when unknown. */
+  fileSize?: number;
+  /** -1 when unknown. */
+  totalBytes?: number;
+  state?: 'in_progress' | 'interrupted' | 'complete';
+}
+
+interface DownloadEvent<L extends (...a: never[]) => void> {
+  addListener(listener: L): void;
+  removeListener(listener: L): void;
+}
+
+export interface DownloadsApiLike {
+  onCreated: DownloadEvent<(item: DownloadItem) => void>;
+  cancel(id: number): Promise<void>;
+  erase(query: { id: number }): Promise<number[]>;
+}
+
+export interface DownloadsSafetyNetDeps {
+  offer: (params: CaptureOfferParams, opts?: { timeoutMs?: number }) => Promise<CaptureOfferResult>;
+  downloads: DownloadsApiLike;
+  getCookies: (url: string) => Promise<CookieRecord[]>;
+  getRules: () => CaptureRules;
+  /** True when the header hook already offered this URL. */
+  wasOffered?: (url: string) => boolean;
+  onOffered?: (url: string) => void;
+  origin?: string;
+  budgetMs?: number;
+}
+
+/** Why the safety net did or did not act on a created download — for the popup diagnostics. */
+export type SafetyNetOutcome =
+  | 'taken' // offered and the daemon took it; Firefox's copy was cancelled + erased
+  | 'offer_declined' // offered, daemon replied ignore
+  | 'error' // fail-open: something threw, Firefox keeps the download
+  | 'capture_disabled'
+  | 'blob_or_data'
+  | 'excluded_host'
+  | 'already_offered'
+  | 'already_settled'
+  | 'no_rule_matched';
+
+type VetoOutcome = Exclude<SafetyNetOutcome, 'taken' | 'offer_declined' | 'error'>;
+
+const BUDGET_MS = 750;
+
+export class DownloadsSafetyNet {
+  private readonly budgetMs: number;
+  private bound?: (item: DownloadItem) => void;
+  private attachedTo?: DownloadsApiLike;
+
+  constructor(private readonly deps: DownloadsSafetyNetDeps) {
+    this.budgetMs = deps.budgetMs ?? BUDGET_MS;
+  }
+
+  attach(downloads: DownloadsApiLike): void {
+    if (this.attachedTo) throw new Error('DownloadsSafetyNet is already attached');
+    this.attachedTo = downloads;
+    this.bound = (item) => void this.handle(item);
+    downloads.onCreated.addListener(this.bound);
+  }
+
+  detach(): void {
+    if (this.attachedTo && this.bound) this.attachedTo.onCreated.removeListener(this.bound);
+    this.attachedTo = undefined;
+    this.bound = undefined;
+  }
+
+  /** Never throws. Returns what it did, for diagnostics/tests. */
+  async handle(item: DownloadItem): Promise<SafetyNetOutcome> {
+    try {
+      const url = effectiveUrl(item);
+      const decision = this.decide(item, url);
+      if (!decision.capture) return decision.reason;
+
+      let cookies: Cookie[] = [];
+      try {
+        cookies = toWireCookies(await this.deps.getCookies(url));
+      } catch {
+        cookies = [];
+      }
+
+      const params: CaptureOfferParams = {
+        url,
+        method: 'GET', // onCreated does not expose the method, and a POST body can't be replayed
+        tabUrl: item.referrer ?? '',
+        cookies,
+        contentType: item.mime ?? null,
+        contentLength: sizeOf(item),
+        filename: basenameOf(item.filename) ?? guessFilename(url, undefined),
+        referrer: item.referrer ?? null,
+        origin: this.deps.origin ?? null,
+      };
+
+      this.deps.onOffered?.(url);
+      const result = await this.deps.offer(params, { timeoutMs: this.budgetMs });
+      if (result.action !== 'take') return 'offer_declined';
+
+      // The daemon owns it now — retire Firefox's copy. Both best-effort.
+      try {
+        await this.deps.downloads.cancel(item.id);
+      } catch {
+        /* already complete or gone */
+      }
+      try {
+        await this.deps.downloads.erase({ id: item.id });
+      } catch {
+        /* nothing to erase */
+      }
+      return 'taken';
+    } catch {
+      return 'error'; // fail open: Firefox keeps the download
+    }
+  }
+
+  private decide(item: DownloadItem, url: string): { capture: true } | { capture: false; reason: VetoOutcome } {
+    const veto = (reason: VetoOutcome) => ({ capture: false as const, reason });
+    const rules = this.deps.getRules();
+    if (!rules.enabled) return veto('capture_disabled');
+    if (/^(blob:|data:)/i.test(url)) return veto('blob_or_data');
+    if (item.state === 'complete' || item.state === 'interrupted') return veto('already_settled');
+    if (this.deps.wasOffered?.(url)) return veto('already_offered');
+
+    const host = hostOf(url);
+    if (host && hostExcluded(host, rules.excludedHosts)) return veto('excluded_host');
+
+    const ext = filenameExtension(basenameOf(item.filename) ?? url);
+    if (ext && rules.monitoredExtensions.includes(ext)) return { capture: true };
+    if (item.mime && rules.monitoredMimeTypes.includes(item.mime.toLowerCase())) return { capture: true };
+
+    const size = sizeOf(item);
+    if (size !== null && size > rules.minSizeBytes) return { capture: true };
+
+    return veto('no_rule_matched');
+  }
+}
+
+// --- helpers ----------------------------------------------------------------------
+
+function effectiveUrl(item: DownloadItem): string {
+  return item.finalUrl && item.finalUrl.length > 0 ? item.finalUrl : item.url;
+}
+
+function sizeOf(item: DownloadItem): number | null {
+  for (const v of [item.totalBytes, item.fileSize]) {
+    if (typeof v === 'number' && v > 0) return v;
+  }
+  return null;
+}
+
+function basenameOf(filename: string | undefined): string | undefined {
+  if (!filename) return undefined;
+  const base = filename.split(/[\\/]/).pop();
+  return base && base.length > 0 ? base : undefined;
+}
+
+function hostOf(url: string): string {
+  try {
+    return new URL(url).hostname;
+  } catch {
+    return '';
+  }
+}
diff --git a/extension/src/background/capture/index.ts b/extension/src/background/capture/index.ts
new file mode 100644
index 0000000..c2ed05c
--- /dev/null
+++ b/extension/src/background/capture/index.ts
@@ -0,0 +1,232 @@
+// The blocking onHeadersReceived hook.
+//
+// For a response that shouldCapture() likes: gather cookies, offer it to the daemon with
+// a hard 750 ms budget, and cancel the browser's own download ONLY on an explicit
+// {action:"take"}. Everything else — shouldCapture says no, the daemon is down / slow /
+// erroring, cookies fail, anything throws — resolves to {} and Firefox downloads
+// normally. Fail-open is not a fallback path here; it is the default every branch returns
+// to. tests/capture/hook.test.ts pins that.
+
+import type {
+  CaptureOfferParams,
+  CaptureOfferResult,
+  CaptureRules,
+  Cookie,
+} from '../../shared/protocol/index.js';
+
+import { normalizeHeaders } from './headers.js';
+import type { HeaderStash } from './headers.js';
+import { filenameExtension, shouldCapture, type CaptureCandidate, type ResourceType } from './rules.js';
+
+const BUDGET_MS = 750; // docs/05 §2 and METHODS['capture.offer'].deadlineMs
+const PROCEED: BlockingResponse = {};
+const CANCEL: BlockingResponse = { cancel: true };
+
+export interface BlockingResponse {
+  cancel?: boolean;
+}
+
+export interface OnHeadersReceivedDetails {
+  requestId: string;
+  url: string;
+  method: string;
+  type: ResourceType;
+  statusCode: number;
+  tabId: number;
+  responseHeaders?: { name: string; value?: string }[];
+  documentUrl?: string | null;
+  originUrl?: string | null;
+}
+
+interface WebRequestEvent<L extends (...a: never[]) => void> {
+  addListener(listener: L, filter: { urls: string[] }, extraInfoSpec?: string[]): void;
+  removeListener(listener: L): void;
+}
+
+export interface HeadersReceivedWebRequest {
+  onHeadersReceived: WebRequestEvent<
+    (d: OnHeadersReceivedDetails) => BlockingResponse | Promise<BlockingResponse>
+  >;
+}
+
+/** A browser cookie, as `browser.cookies.getAll` returns it (superset of the wire type). */
+export interface CookieRecord {
+  name: string;
+  value: string;
+  domain?: string;
+  path?: string;
+  secure?: boolean;
+  httpOnly?: boolean;
+}
+
+export interface CaptureHookDeps {
+  /** Usually `(p, o) => transport.call('capture.offer', p, o)`. */
+  offer: (params: CaptureOfferParams, opts?: { timeoutMs?: number }) => Promise<CaptureOfferResult>;
+  stash: Pick<HeaderStash, 'take' | 'peek'>;
+  getCookies: (url: string) => Promise<CookieRecord[]>;
+  /** A synchronous snapshot of the daemon's capture policy (mirrored via capture.getRules). */
+  getRules: () => CaptureRules;
+  /** Whether the user held the bypass modifier for the click behind this request. */
+  bypassHeld?: (details: OnHeadersReceivedDetails) => boolean;
+  /** Called with the URL just before an offer is made, so the downloads.onCreated safety
+   *  net can tell this request has already been handled here. */
+  onOffered?: (url: string) => void;
+  /** moz-extension://<uuid>, for CaptureOfferParams.origin. */
+  origin?: string;
+  budgetMs?: number;
+}
+
+const ALL_URLS = '<all_urls>';
+
+export class CaptureHook {
+  private readonly budgetMs: number;
+  private bound?: (d: OnHeadersReceivedDetails) => Promise<BlockingResponse>;
+  private attachedTo?: HeadersReceivedWebRequest;
+
+  constructor(private readonly deps: CaptureHookDeps) {
+    this.budgetMs = deps.budgetMs ?? BUDGET_MS;
+  }
+
+  /** The listener. Always resolves within the budget to {} or {cancel:true}; never rejects. */
+  handle = (details: OnHeadersReceivedDetails): Promise<BlockingResponse> => {
+    return this.withinBudget(this.decide(details));
+  };
+
+  attach(webRequest: HeadersReceivedWebRequest): void {
+    if (this.attachedTo) throw new Error('CaptureHook is already attached');
+    this.attachedTo = webRequest;
+    this.bound = this.handle;
+    webRequest.onHeadersReceived.addListener(this.bound, { urls: [ALL_URLS] }, [
+      'blocking',
+      'responseHeaders',
+    ]);
+  }
+
+  detach(): void {
+    if (this.attachedTo && this.bound) {
+      this.attachedTo.onHeadersReceived.removeListener(this.bound);
+    }
+    this.attachedTo = undefined;
+    this.bound = undefined;
+  }
+
+  private withinBudget(work: Promise<BlockingResponse>): Promise<BlockingResponse> {
+    return new Promise<BlockingResponse>((resolve) => {
+      let settled = false;
+      const done = (value: BlockingResponse): void => {
+        if (settled) return;
+        settled = true;
+        clearTimeout(timer);
+        resolve(value);
+      };
+      const timer = setTimeout(() => done(PROCEED), this.budgetMs);
+      (timer as { unref?: () => void }).unref?.();
+      work.then(done, () => done(PROCEED));
+    });
+  }
+
+  private async decide(details: OnHeadersReceivedDetails): Promise<BlockingResponse> {
+    try {
+      const rules = this.deps.getRules();
+      const responseHeaders = normalizeHeaders(details.responseHeaders);
+      const stashed = this.stashPeek(details.requestId);
+
+      const candidate: CaptureCandidate = {
+        url: details.url,
+        method: details.method,
+        statusCode: details.statusCode,
+        type: details.type,
+        responseHeaders,
+        requestHeaders: stashed?.headers ?? {},
+        documentUrl: details.documentUrl ?? details.originUrl ?? null,
+        bypassHeld: this.deps.bypassHeld?.(details) ?? false,
+      };
+
+      if (!shouldCapture(candidate, rules).capture) return PROCEED;
+
+      // We are acting on this request now — take the stash entry.
+      const taken = this.deps.stash.take(details.requestId);
+      const requestHeaders = taken?.headers ?? candidate.requestHeaders;
+
+      let cookies: Cookie[] = [];
+      try {
+        cookies = toWireCookies(await this.deps.getCookies(details.url));
+      } catch {
+        cookies = []; // best-effort; still worth offering
+      }
+
+      const params: CaptureOfferParams = {
+        url: details.url,
+        method: candidate.method.toUpperCase() === 'POST' ? 'POST' : 'GET',
+        tabUrl: candidate.documentUrl ?? '',
+        headers: requestHeaders,
+        cookies,
+        contentType: responseHeaders['content-type'] ?? null,
+        contentLength: intOrNull(responseHeaders['content-length']),
+        contentDisposition: responseHeaders['content-disposition'] ?? null,
+        filename: guessFilename(details.url, responseHeaders['content-disposition']),
+        referrer: requestHeaders['referer'] ?? null,
+        origin: this.deps.origin ?? null,
+        requestId: details.requestId,
+      };
+
+      this.deps.onOffered?.(details.url);
+      const result = await this.deps.offer(params, { timeoutMs: this.budgetMs });
+      return result.action === 'take' ? CANCEL : PROCEED;
+    } catch {
+      return PROCEED; // fail open on anything at all
+    }
+  }
+
+  private stashPeek(requestId: string) {
+    try {
+      return this.deps.stash.peek(requestId);
+    } catch {
+      return undefined;
+    }
+  }
+}
+
+// --- helpers ----------------------------------------------------------------------
+
+export function toWireCookies(records: CookieRecord[]): Cookie[] {
+  return records.map((c) => {
+    const out: Cookie = { name: c.name, value: c.value };
+    if (c.domain !== undefined) out.domain = c.domain;
+    if (c.path !== undefined) out.path = c.path;
+    if (c.secure !== undefined) out.secure = c.secure;
+    if (c.httpOnly !== undefined) out.httpOnly = c.httpOnly;
+    return out;
+  });
+}
+
+function intOrNull(value: string | undefined): number | null {
+  if (value === undefined) return null;
+  const n = Number(value);
+  return Number.isFinite(n) ? n : null;
+}
+
+/** RFC 6266 filename, falling back to the URL's last path segment. */
+export function guessFilename(url: string, disposition: string | undefined): string | null {
+  if (disposition) {
+    const star = /filename\*\s*=\s*(?:[^']*'[^']*')?([^;]+)/i.exec(disposition);
+    if (star?.[1]) {
+      try {
+        return decodeURIComponent(star[1].trim().replace(/^"|"$/g, '')) || null;
+      } catch {
+        /* fall through */
+      }
+    }
+    const plain = /filename\s*=\s*"?([^";]+)"?/i.exec(disposition);
+    if (plain?.[1]) return plain[1].trim() || null;
+  }
+  try {
+    const path = new URL(url).pathname;
+    const base = decodeURIComponent(path.slice(path.lastIndexOf('/') + 1));
+    if (base) return base;
+  } catch {
+    /* not a parseable URL */
+  }
+  const ext = filenameExtension(url);
+  return ext ? `download.${ext}` : null;
+}
diff --git a/extension/src/background/capture/offered-urls.ts b/extension/src/background/capture/offered-urls.ts
new file mode 100644
index 0000000..7c4918a
--- /dev/null
+++ b/extension/src/background/capture/offered-urls.ts
@@ -0,0 +1,51 @@
+// A short-lived record of URLs the header hook has already offered to the daemon, so the
+// downloads.onCreated safety net does not offer the same thing a second time.
+//
+// Bounded and time-capped for the same reason the header stash is (capture/headers.ts):
+// this sees a URL for every capture attempt and must never grow without bound.
+
+export interface OfferedUrlsOptions {
+  /** Entries older than this stop counting as "recently offered". Default 15 s. */
+  ttlMs?: number;
+  /** Hard cap on tracked URLs; oldest evicted past it. Default 256. */
+  maxEntries?: number;
+  now?: () => number;
+}
+
+export class OfferedUrls {
+  private readonly ttlMs: number;
+  private readonly maxEntries: number;
+  private readonly now: () => number;
+  /** url -> timestamp, insertion-ordered so the first key is the oldest. */
+  private readonly seen = new Map<string, number>();
+
+  constructor(opts: OfferedUrlsOptions = {}) {
+    this.ttlMs = opts.ttlMs ?? 15_000;
+    this.maxEntries = opts.maxEntries ?? 256;
+    this.now = opts.now ?? Date.now;
+  }
+
+  mark(url: string): void {
+    this.seen.delete(url);
+    this.seen.set(url, this.now());
+    while (this.seen.size > this.maxEntries) {
+      const oldest = this.seen.keys().next().value;
+      if (oldest === undefined) break;
+      this.seen.delete(oldest);
+    }
+  }
+
+  has(url: string): boolean {
+    const at = this.seen.get(url);
+    if (at === undefined) return false;
+    if (this.now() - at > this.ttlMs) {
+      this.seen.delete(url);
+      return false;
+    }
+    return true;
+  }
+
+  get size(): number {
+    return this.seen.size;
+  }
+}
diff --git a/extension/src/background/capture/rules.ts b/extension/src/background/capture/rules.ts
index 339e091..96b7bef 100644
--- a/extension/src/background/capture/rules.ts
+++ b/extension/src/background/capture/rules.ts
@@ -63,6 +63,19 @@ export interface CaptureDecision {
   reason: CaptureReason;
 }
 
+/**
+ * What shouldCapture() runs against before the first capture.getRules has been mirrored
+ * from the daemon. `enabled: false` — we intercept nothing until we know the real policy.
+ */
+export const DEFAULT_CAPTURE_RULES: CaptureRules = {
+  enabled: false,
+  monitoredExtensions: [],
+  monitoredMimeTypes: [],
+  minSizeBytes: 1024 * 1024,
+  excludedHosts: [],
+  rulesVersion: 0,
+};
+
 const RENDERABLE_TYPES = new Set([
   'text/html',
   'application/xhtml+xml',
diff --git a/extension/src/background/context-menus.ts b/extension/src/background/context-menus.ts
new file mode 100644
index 0000000..c9d9d73
--- /dev/null
+++ b/extension/src/background/context-menus.ts
@@ -0,0 +1,123 @@
+// Right-click and keyboard entry points.
+//
+// docs/05 §3: "Download with Velox" on a link or a media element hands that one URL to
+// the daemon; a configurable command grabs the active tab's URL the same way. The
+// page/selection "Download all links…" item waits on the content-script link harvester
+// (build-order step 7) and is added there.
+//
+// These are explicit user requests, so they go straight to download.add — no
+// shouldCapture, no fail-open dance.
+
+import type { DownloadSpec } from '../shared/protocol/index.js';
+
+export const LINK_MENU_ID = 'velox-download-link';
+export const MEDIA_MENU_ID = 'velox-download-media';
+export const GRAB_TAB_COMMAND = 'velox-grab-current-tab';
+
+interface OnClickedInfo {
+  menuItemId: string | number;
+  linkUrl?: string;
+  srcUrl?: string;
+  pageUrl?: string;
+}
+
+interface Tab {
+  url?: string;
+  title?: string;
+}
+
+interface Listenable<A extends unknown[]> {
+  addListener(cb: (...args: A) => void): void;
+  removeListener(cb: (...args: A) => void): void;
+}
+
+export interface MenusLike {
+  create(props: {
+    id: string;
+    title: string;
+    contexts: string[];
+  }): void;
+  removeAll(): Promise<void> | void;
+  onClicked: Listenable<[OnClickedInfo, Tab | undefined]>;
+}
+
+export interface CommandsLike {
+  onCommand: Listenable<[string, Tab | undefined]>;
+}
+
+export interface TabsLike {
+  query(q: { active: true; currentWindow: true }): Promise<Tab[]>;
+}
+
+export interface ContextMenusDeps {
+  addDownload: (spec: DownloadSpec) => Promise<unknown>;
+  menus: MenusLike;
+  tabs: TabsLike;
+  commands?: CommandsLike;
+  /** Surface a failure to the user (a notification, usually). Optional. */
+  onError?: (message: string) => void;
+}
+
+export class ContextMenus {
+  private onClicked?: (info: OnClickedInfo, tab: Tab | undefined) => void;
+  private onCommand?: (name: string, tab: Tab | undefined) => void;
+
+  constructor(private readonly deps: ContextMenusDeps) {}
+
+  async register(): Promise<void> {
+    await this.deps.menus.removeAll();
+    this.deps.menus.create({ id: LINK_MENU_ID, title: 'Download with Velox', contexts: ['link'] });
+    this.deps.menus.create({
+      id: MEDIA_MENU_ID,
+      title: 'Download with Velox',
+      contexts: ['image', 'video', 'audio'],
+    });
+
+    this.onClicked = (info, tab) => void this.handleClick(info, tab);
+    this.deps.menus.onClicked.addListener(this.onClicked);
+
+    if (this.deps.commands) {
+      this.onCommand = (name, tab) => void this.handleCommand(name, tab);
+      this.deps.commands.onCommand.addListener(this.onCommand);
+    }
+  }
+
+  dispose(): void {
+    if (this.onClicked) this.deps.menus.onClicked.removeListener(this.onClicked);
+    if (this.onCommand && this.deps.commands) this.deps.commands.onCommand.removeListener(this.onCommand);
+    this.onClicked = undefined;
+    this.onCommand = undefined;
+  }
+
+  private async handleClick(info: OnClickedInfo, _tab: Tab | undefined): Promise<void> {
+    let url: string | undefined;
+    if (info.menuItemId === LINK_MENU_ID) url = info.linkUrl;
+    else if (info.menuItemId === MEDIA_MENU_ID) url = info.srcUrl;
+    else return;
+    await this.add(url, info.pageUrl);
+  }
+
+  private async handleCommand(name: string, tab: Tab | undefined): Promise<void> {
+    if (name !== GRAB_TAB_COMMAND) return;
+    const active = tab ?? (await this.deps.tabs.query({ active: true, currentWindow: true }))[0];
+    await this.add(active?.url, active?.url);
+  }
+
+  private async add(url: string | undefined, referrer: string | undefined): Promise<void> {
+    if (!url || !/^https?:/i.test(url)) {
+      this.deps.onError?.('Velox can only download http(s) links.');
+      return;
+    }
+    const spec: DownloadSpec = { url };
+    if (referrer) spec.referrer = referrer;
+    try {
+      await this.deps.addDownload(spec);
+    } catch (err) {
+      this.deps.onError?.(`Velox could not start the download: ${describe(err)}`);
+    }
+  }
+}
+
+function describe(err: unknown): string {
+  return err instanceof Error ? err.message : String(err);
+}
diff --git a/extension/src/background/index.ts b/extension/src/background/index.ts
index eb846c0..ed7df75 100644
--- a/extension/src/background/index.ts
+++ b/extension/src/background/index.ts
@@ -1,20 +1,95 @@
 // Background event-page entry.
 //
-// Brings the transport up and holds the single shared reference to it. Capture, the
-// popup relay, and context menus attach here as they land (docs/05 §6 build order).
+// Brings the transport up, mirrors the daemon's capture rules, and wires both capture
+// paths: the blocking onHeadersReceived hook and the downloads.onCreated safety net. The
+// popup relay and context menus attach here in later steps of the build order.
 
+import { DownloadsSafetyNet, type DownloadsApiLike } from './capture/downloads-api.js';
+import { HeaderStash, type WebRequestLike } from './capture/headers.js';
+import { CaptureHook, type HeadersReceivedWebRequest } from './capture/index.js';
+import { OfferedUrls } from './capture/offered-urls.js';
+import { DEFAULT_CAPTURE_RULES } from './capture/rules.js';
+import {
+  ContextMenus,
+  type CommandsLike,
+  type MenusLike,
+  type TabsLike,
+} from './context-menus.js';
 import { createTransport, type TransportStatus, type VeloxTransport } from './transport/index.js';
+import type { CaptureOfferParams, CaptureRules, DownloadSpec } from '../shared/protocol/index.js';
 
 let transport: VeloxTransport | undefined;
+let rules: CaptureRules = DEFAULT_CAPTURE_RULES;
+
+const EXTENSION_ORIGIN = new URL(browser.runtime.getURL('/')).origin;
+
+function mustTransport(): VeloxTransport {
+  if (!transport) throw new Error('transport not ready');
+  return transport;
+}
+
+const offer = (params: CaptureOfferParams, opts?: { timeoutMs?: number }) =>
+  mustTransport().call('capture.offer', params, opts);
+const getCookies = (url: string) => browser.cookies.getAll({ url });
+
+const offered = new OfferedUrls();
+const stash = new HeaderStash();
+
+const hook = new CaptureHook({
+  offer,
+  stash,
+  getCookies,
+  getRules: () => rules,
+  onOffered: (url) => offered.mark(url),
+  origin: EXTENSION_ORIGIN,
+});
+
+const safetyNet = new DownloadsSafetyNet({
+  offer,
+  downloads: browser.downloads as unknown as DownloadsApiLike,
+  getCookies,
+  getRules: () => rules,
+  wasOffered: (url) => offered.has(url),
+  onOffered: (url) => offered.mark(url),
+  origin: EXTENSION_ORIGIN,
+});
+
+const contextMenus = new ContextMenus({
+  addDownload: (spec: DownloadSpec) => mustTransport().call('download.add', spec),
+  menus: browser.contextMenus as unknown as MenusLike,
+  tabs: browser.tabs as unknown as TabsLike,
+  commands: browser.commands as unknown as CommandsLike,
+  onError: (message) => {
+    void browser.notifications.create({ type: 'basic', title: 'Velox', message });
+  },
+});
+
+async function refreshRules(): Promise<void> {
+  try {
+    rules = await mustTransport().call('capture.getRules', {});
+  } catch {
+    // Keep the last known rules; capture stays fail-open regardless (docs/05 §2).
+  }
+}
 
 function onTransportState(status: TransportStatus): void {
   const detail = status.fatal ?? (status.needsPairing ? 'needs pairing' : '');
   console.debug(`[velox] transport ${status.state}${detail ? ` — ${detail}` : ''}`);
+  if (status.state === 'connected') void refreshRules();
 }
 
 async function start(): Promise<void> {
+  stash.attach(browser.webRequest as unknown as WebRequestLike);
+  hook.attach(browser.webRequest as unknown as HeadersReceivedWebRequest);
+  safetyNet.attach(browser.downloads as unknown as DownloadsApiLike);
+  void contextMenus.register();
+
   transport = await createTransport();
   transport.onStateChange(onTransportState);
+  transport.on('event.settings.changed', (payload) => {
+    const keys = (payload as { keys?: string[] }).keys ?? [];
+    if (keys.some((k) => k.startsWith('capture.'))) void refreshRules();
+  });
   onTransportState(transport.status);
 }
 
diff --git a/extension/tests/capture/downloads-api.test.ts b/extension/tests/capture/downloads-api.test.ts
new file mode 100644
index 0000000..5e94a6d
--- /dev/null
+++ b/extension/tests/capture/downloads-api.test.ts
@@ -0,0 +1,174 @@
+import { describe, expect, it, vi } from 'vitest';
+
+import type { CaptureOfferParams, CaptureOfferResult, CaptureRules } from '../../src/shared/protocol/index.js';
+import {
+  DownloadsSafetyNet,
+  type DownloadItem,
+  type DownloadsApiLike,
+  type DownloadsSafetyNetDeps,
+} from '../../src/background/capture/downloads-api.js';
+
+const RULES: CaptureRules = {
+  enabled: true,
+  monitoredExtensions: ['zip', 'iso'],
+  monitoredMimeTypes: ['application/octet-stream'],
+  minSizeBytes: 1024 * 1024,
+  excludedHosts: ['mail.example.com'],
+  rulesVersion: 1,
+};
+
+function item(over: Partial<DownloadItem> = {}): DownloadItem {
+  return {
+    id: 5,
+    url: 'https://cdn.example.com/pkg/tool.zip',
+    finalUrl: 'https://cdn.example.com/pkg/tool.zip',
+    referrer: 'https://example.com/get',
+    filename: '/home/u/Downloads/tool.zip',
+    mime: 'application/zip',
+    fileSize: -1,
+    totalBytes: 50 * 1024 * 1024,
+    state: 'in_progress',
+    ...over,
+  };
+}
+
+interface Harness {
+  net: DownloadsSafetyNet;
+  offer: ReturnType<typeof vi.fn>;
+  cancel: ReturnType<typeof vi.fn>;
+  erase: ReturnType<typeof vi.fn>;
+  seen: CaptureOfferParams[];
+}
+
+function makeNet(over: Partial<DownloadsSafetyNetDeps> = {}): Harness {
+  const seen: CaptureOfferParams[] = [];
+  const offer =
+    (over.offer as ReturnType<typeof vi.fn> | undefined) ??
+    vi.fn(async (p: CaptureOfferParams): Promise<CaptureOfferResult> => {
+      seen.push(p);
+      return { action: 'take', taskId: 't1' };
+    });
+  const cancel = vi.fn(async () => undefined);
+  const erase = vi.fn(async () => [5]);
+  const downloads = { onCreated: { addListener: vi.fn(), removeListener: vi.fn() }, cancel, erase } as unknown as DownloadsApiLike;
+  const deps: DownloadsSafetyNetDeps = {
+    offer: offer as unknown as DownloadsSafetyNetDeps['offer'],
+    downloads,
+    getCookies: vi.fn(async () => [{ name: 'sid', value: 'x' }]) as unknown as DownloadsSafetyNetDeps['getCookies'],
+    getRules: () => RULES,
+    origin: 'moz-extension://uuid',
+    ...over,
+  };
+  return { net: new DownloadsSafetyNet(deps), offer: offer as ReturnType<typeof vi.fn>, cancel, erase, seen };
+}
+
+describe('DownloadsSafetyNet.decide', () => {
+  it('offers a monitored-extension download and, on take, cancels + erases it', async () => {
+    const { net, cancel, erase, seen } = makeNet();
+    await expect(net.handle(item({ mime: 'application/zip' }))).resolves.toBe('taken');
+    expect(seen[0]).toMatchObject({
+      url: 'https://cdn.example.com/pkg/tool.zip',
+      method: 'GET',
+      filename: 'tool.zip',
+      contentLength: 50 * 1024 * 1024,
+      referrer: 'https://example.com/get',
+      origin: 'moz-extension://uuid',
+    });
+    expect(cancel).toHaveBeenCalledWith(5);
+    expect(erase).toHaveBeenCalledWith({ id: 5 });
+  });
+
+  it('offers on the size threshold alone', async () => {
+    const { net } = makeNet();
+    await expect(
+      net.handle(item({ filename: 'blob.bin', url: 'https://cdn.example.com/x', finalUrl: '', mime: 'application/x-thing', totalBytes: 9 * 1024 * 1024 })),
+    ).resolves.toBe('taken');
+  });
+
+  it('leaves blob: downloads to Firefox', async () => {
+    const { net, offer } = makeNet();
+    await expect(net.handle(item({ url: 'blob:https://example.com/abc', finalUrl: '' }))).resolves.toBe('blob_or_data');
+    expect(offer).not.toHaveBeenCalled();
+  });
+
+  it('skips an excluded host', async () => {
+    const { net } = makeNet();
+    await expect(
+      net.handle(item({ url: 'https://mail.example.com/a.zip', finalUrl: 'https://mail.example.com/a.zip' })),
+    ).resolves.toBe('excluded_host');
+  });
+
+  it('skips a download that already completed or was interrupted', async () => {
+    const { net } = makeNet();
+    await expect(net.handle(item({ state: 'complete' }))).resolves.toBe('already_settled');
+    await expect(net.handle(item({ state: 'interrupted' }))).resolves.toBe('already_settled');
+  });
+
+  it('skips a URL the header hook already offered', async () => {
+    const { net, offer } = makeNet({ wasOffered: (u) => u === 'https://cdn.example.com/pkg/tool.zip' });
+    await expect(net.handle(item())).resolves.toBe('already_offered');
+    expect(offer).not.toHaveBeenCalled();
+  });
+
+  it('skips when capture is disabled', async () => {
+    const { net } = makeNet({ getRules: () => ({ ...RULES, enabled: false }) });
+    await expect(net.handle(item())).resolves.toBe('capture_disabled');
+  });
+
+  it('skips a small file that matches no rule', async () => {
+    const { net } = makeNet();
+    await expect(
+      net.handle(item({ filename: 'note.txt', url: 'https://cdn.example.com/note.txt', finalUrl: '', mime: 'text/plain', totalBytes: 200 })),
+    ).resolves.toBe('no_rule_matched');
+  });
+});
+
+describe('DownloadsSafetyNet — fail-open', () => {
+  it('offer() rejects → the Firefox download is left completely alone', async () => {
+    const { net, cancel, erase } = makeNet({
+      offer: vi.fn().mockRejectedValue(new Error('daemon down')) as unknown as DownloadsSafetyNetDeps['offer'],
+    });
+    await expect(net.handle(item())).resolves.toBe('error');
+    expect(cancel).not.toHaveBeenCalled();
+    expect(erase).not.toHaveBeenCalled();
+  });
+
+  it('offer() → ignore leaves the download alone', async () => {
+    const { net, cancel } = makeNet({
+      offer: vi.fn(async () => ({ action: 'ignore', reason: 'below_min_size' })) as unknown as DownloadsSafetyNetDeps['offer'],
+    });
+    await expect(net.handle(item())).resolves.toBe('offer_declined');
+    expect(cancel).not.toHaveBeenCalled();
+  });
+
+  it('cancel() throwing after a take does not throw out of handle()', async () => {
+    const { net, erase } = makeNet();
+    (net as unknown as { deps: DownloadsSafetyNetDeps }).deps.downloads.cancel = vi
+      .fn()
+      .mockRejectedValue(new Error('already complete'));
+    await expect(net.handle(item())).resolves.toBe('taken');
+    expect(erase).toHaveBeenCalled(); // still tries to erase
+  });
+
+  it('still offers with an empty cookie list when cookie collection fails', async () => {
+    const { net, seen } = makeNet({
+      getCookies: vi.fn().mockRejectedValue(new Error('no perm')) as unknown as DownloadsSafetyNetDeps['getCookies'],
+    });
+    await expect(net.handle(item())).resolves.toBe('taken');
+    expect(seen[0]!.cookies).toEqual([]);
+  });
+});
+
+describe('DownloadsSafetyNet.attach', () => {
+  it('registers and unregisters an onCreated listener', () => {
+    const add = vi.fn();
+    const remove = vi.fn();
+    const downloads = { onCreated: { addListener: add, removeListener: remove }, cancel: vi.fn(), erase: vi.fn() } as unknown as DownloadsApiLike;
+    const { net } = makeNet();
+    net.attach(downloads);
+    expect(add).toHaveBeenCalledOnce();
+    expect(() => net.attach(downloads)).toThrow(/already attached/);
+    net.detach();
+    expect(remove).toHaveBeenCalledOnce();
+  });
+});
diff --git a/extension/tests/capture/hook.test.ts b/extension/tests/capture/hook.test.ts
new file mode 100644
index 0000000..f1d7621
--- /dev/null
+++ b/extension/tests/capture/hook.test.ts
@@ -0,0 +1,199 @@
+// The blocking onHeadersReceived hook.
+//
+// Fail-open is the hard requirement (docs/05 §2, AGENT-EXT M1 DoD): daemon down, slow, or
+// erroring must never cost the user a download. Those cases are written first below.
+
+import { afterEach, describe, expect, it, vi } from 'vitest';
+
+import type { CaptureOfferParams, CaptureOfferResult, CaptureRules } from '../../src/shared/protocol/index.js';
+import {
+  CaptureHook,
+  type CaptureHookDeps,
+  type HeadersReceivedWebRequest,
+  type OnHeadersReceivedDetails,
+} from '../../src/background/capture/index.js';
+
+const RULES: CaptureRules = {
+  enabled: true,
+  monitoredExtensions: ['zip', 'iso'],
+  monitoredMimeTypes: ['application/octet-stream'],
+  minSizeBytes: 1024 * 1024,
+  excludedHosts: [],
+  rulesVersion: 1,
+};
+
+function detailsFor(over: Partial<OnHeadersReceivedDetails> = {}): OnHeadersReceivedDetails {
+  return {
+    requestId: '42',
+    url: 'https://cdn.example.com/files/ubuntu.iso',
+    method: 'GET',
+    type: 'other',
+    statusCode: 200,
+    tabId: 3,
+    responseHeaders: [
+      { name: 'Content-Type', value: 'application/octet-stream' },
+      { name: 'Content-Length', value: String(900 * 1024 * 1024) },
+    ],
+    documentUrl: 'https://example.com/releases',
+    ...over,
+  };
+}
+
+interface Harness {
+  hook: CaptureHook;
+  offer: ReturnType<typeof vi.fn>;
+  stash: { take: ReturnType<typeof vi.fn>; peek: ReturnType<typeof vi.fn> };
+  getCookies: ReturnType<typeof vi.fn>;
+}
+
+function makeHook(over: Partial<CaptureHookDeps> = {}): Harness {
+  const { offer: offerOver, getCookies: cookiesOver, stash: stashOver, ...rest } = over;
+  const stashEntry = { requestId: '42', url: '', method: 'GET', tabId: 3, stashedAt: 0, headers: { referer: 'https://example.com/releases' } };
+  const stash = (stashOver as unknown as Harness['stash']) ?? {
+    take: vi.fn(() => stashEntry),
+    peek: vi.fn(() => stashEntry),
+  };
+  const offer =
+    (offerOver as unknown as ReturnType<typeof vi.fn>) ??
+    vi.fn(async (): Promise<CaptureOfferResult> => ({ action: 'ignore', reason: 'type_not_monitored' }));
+  const getCookies =
+    (cookiesOver as unknown as ReturnType<typeof vi.fn>) ??
+    vi.fn(async () => [{ name: 'sid', value: 'abc', domain: '.example.com', secure: true }]);
+  const deps: CaptureHookDeps = {
+    offer: offer as unknown as CaptureHookDeps['offer'],
+    stash: stash as unknown as CaptureHookDeps['stash'],
+    getCookies: getCookies as unknown as CaptureHookDeps['getCookies'],
+    getRules: () => RULES,
+    origin: 'moz-extension://11111111-2222-3333-4444-555555555555',
+    budgetMs: 40,
+    ...rest,
+  };
+  return { hook: new CaptureHook(deps), offer, stash, getCookies };
+}
+
+afterEach(() => {
+  vi.useRealTimers();
+});
+
+describe('CaptureHook — fail-open (written before the feature)', () => {
+  it('daemon down: offer() rejects → Firefox downloads normally', async () => {
+    const { hook } = makeHook({ offer: vi.fn().mockRejectedValue(new Error('transport is not connected')) });
+    await expect(hook.handle(detailsFor())).resolves.toEqual({});
+  });
+
+  it('daemon slow: offer() never settles → resolves to {} within the budget', async () => {
+    const { hook } = makeHook({ offer: vi.fn(() => new Promise<never>(() => {})), budgetMs: 30 });
+    const started = Date.now();
+    await expect(hook.handle(detailsFor())).resolves.toEqual({});
+    expect(Date.now() - started).toBeGreaterThanOrEqual(20);
+    expect(Date.now() - started).toBeLessThan(300);
+  });
+
+  it('daemon erroring: offer() rejects with a timeout-like error → {}', async () => {
+    const err = Object.assign(new Error('capture.offer timed out after 750 ms'), { name: 'RpcTimeoutError' });
+    const { hook } = makeHook({ offer: vi.fn().mockRejectedValue(err) });
+    await expect(hook.handle(detailsFor())).resolves.toEqual({});
+  });
+
+  it('getRules() throws → {} and no offer attempted', async () => {
+    const offer = vi.fn();
+    const { hook } = makeHook({
+      offer: offer as unknown as CaptureHookDeps['offer'],
+      getRules: () => {
+        throw new Error('rules not loaded');
+      },
+    });
+    await expect(hook.handle(detailsFor())).resolves.toEqual({});
+    expect(offer).not.toHaveBeenCalled();
+  });
+
+  it('the listener never rejects, whatever the details', async () => {
+    const { hook } = makeHook();
+    // @ts-expect-error deliberately malformed
+    await expect(hook.handle({})).resolves.toEqual({});
+  });
+});
+
+describe('CaptureHook — the happy paths', () => {
+  it('shouldCapture says no → {} and the offer is not made, stash not consumed', async () => {
+    const { hook, offer, stash } = makeHook({ getRules: () => ({ ...RULES, enabled: false }) });
+    await expect(hook.handle(detailsFor())).resolves.toEqual({});
+    expect(offer).not.toHaveBeenCalled();
+    expect(stash.take).not.toHaveBeenCalled();
+  });
+
+  it('offer → {action:"take"} cancels the browser download', async () => {
+    const { hook, offer, stash } = makeHook({
+      offer: vi.fn(async () => ({ action: 'take', taskId: 't1' })) as unknown as CaptureHookDeps['offer'],
+    });
+    await expect(hook.handle(detailsFor())).resolves.toEqual({ cancel: true });
+    expect(offer).toHaveBeenCalledOnce();
+    expect(stash.take).toHaveBeenCalledWith('42');
+  });
+
+  it('offer → {action:"ignore"} lets Firefox proceed', async () => {
+    const { hook } = makeHook();
+    await expect(hook.handle(detailsFor())).resolves.toEqual({});
+  });
+
+  it('builds a well-formed capture.offer from details + stash + response headers', async () => {
+    const seen: CaptureOfferParams[] = [];
+    const { hook } = makeHook({
+      offer: (vi.fn(async (p: CaptureOfferParams) => {
+        seen.push(p);
+        return { action: 'take', taskId: 't' };
+      }) as unknown) as CaptureHookDeps['offer'],
+    });
+    await hook.handle(detailsFor());
+    expect(seen[0]).toMatchObject({
+      url: 'https://cdn.example.com/files/ubuntu.iso',
+      method: 'GET',
+      tabUrl: 'https://example.com/releases',
+      contentType: 'application/octet-stream',
+      contentLength: 900 * 1024 * 1024,
+      referrer: 'https://example.com/releases',
+      origin: 'moz-extension://11111111-2222-3333-4444-555555555555',
+      requestId: '42',
+      filename: 'ubuntu.iso',
+    });
+    expect(seen[0]!.cookies).toEqual([{ name: 'sid', value: 'abc', domain: '.example.com', secure: true }]);
+  });
+
+  it('still offers when cookie collection fails, with an empty cookie list', async () => {
+    const seen: CaptureOfferParams[] = [];
+    const { hook } = makeHook({
+      offer: (async (p: CaptureOfferParams) => {
+        seen.push(p);
+        return { action: 'take', taskId: 't' };
+      }) as CaptureHookDeps['offer'],
+      getCookies: (async () => {
+        throw new Error('no cookies perm');
+      }) as CaptureHookDeps['getCookies'],
+    });
+    await expect(hook.handle(detailsFor())).resolves.toEqual({ cancel: true });
+    expect(seen[0]!.cookies).toEqual([]);
+  });
+});
+
+describe('CaptureHook.attach', () => {
+  class FakeEvent {
+    listeners: Array<(d: OnHeadersReceivedDetails) => unknown> = [];
+    addListener = (l: (d: OnHeadersReceivedDetails) => unknown): void => void this.listeners.push(l);
+    removeListener = (l: (d: OnHeadersReceivedDetails) => unknown): void => {
+      this.listeners = this.listeners.filter((x) => x !== l);
+    };
+  }
+
+  it('registers a blocking responseHeaders listener and unregisters on detach', () => {
+    const evt = new FakeEvent();
+    const wr = { onHeadersReceived: evt } as unknown as HeadersReceivedWebRequest;
+    const { hook } = makeHook();
+
+    hook.attach(wr);
+    expect(evt.listeners).toHaveLength(1);
+    expect(() => hook.attach(wr)).toThrow(/already attached/);
+
+    hook.detach();
+    expect(evt.listeners).toHaveLength(0);
+  });
+});
diff --git a/extension/tests/capture/offered-urls.test.ts b/extension/tests/capture/offered-urls.test.ts
new file mode 100644
index 0000000..dcecf30
--- /dev/null
+++ b/extension/tests/capture/offered-urls.test.ts
@@ -0,0 +1,39 @@
+import { describe, expect, it } from 'vitest';
+
+import { OfferedUrls } from '../../src/background/capture/offered-urls.js';
+
+describe('OfferedUrls', () => {
+  it('remembers a URL for the TTL, then forgets it', () => {
+    let now = 0;
+    const o = new OfferedUrls({ ttlMs: 1000, now: () => now });
+    o.mark('https://x/a.zip');
+    expect(o.has('https://x/a.zip')).toBe(true);
+    now = 1001;
+    expect(o.has('https://x/a.zip')).toBe(false);
+    expect(o.size).toBe(0);
+  });
+
+  it('re-mark refreshes the TTL', () => {
+    let now = 0;
+    const o = new OfferedUrls({ ttlMs: 1000, now: () => now });
+    o.mark('u');
+    now = 900;
+    o.mark('u');
+    now = 1800; // 900 since the last mark
+    expect(o.has('u')).toBe(true);
+  });
+
+  it('evicts the oldest past the size cap', () => {
+    const o = new OfferedUrls({ maxEntries: 2, ttlMs: 10_000, now: () => 0 });
+    o.mark('a');
+    o.mark('b');
+    o.mark('c');
+    expect(o.has('a')).toBe(false);
+    expect(o.has('b')).toBe(true);
+    expect(o.has('c')).toBe(true);
+  });
+
+  it('is false for a URL it has never seen', () => {
+    expect(new OfferedUrls().has('nope')).toBe(false);
+  });
+});
diff --git a/extension/tests/context-menus.test.ts b/extension/tests/context-menus.test.ts
new file mode 100644
index 0000000..f1bcf13
--- /dev/null
+++ b/extension/tests/context-menus.test.ts
@@ -0,0 +1,134 @@
+import { describe, expect, it, vi } from 'vitest';
+
+import type { DownloadSpec } from '../src/shared/protocol/index.js';
+import {
+  ContextMenus,
+  GRAB_TAB_COMMAND,
+  LINK_MENU_ID,
+  MEDIA_MENU_ID,
+  type ContextMenusDeps,
+} from '../src/background/context-menus.js';
+
+class Event<A extends unknown[]> {
+  fns: Array<(...a: A) => void> = [];
+  addListener = (f: (...a: A) => void): void => void this.fns.push(f);
+  removeListener = (f: (...a: A) => void): void => {
+    this.fns = this.fns.filter((x) => x !== f);
+  };
+  emit(...a: A): void {
+    for (const f of this.fns) f(...a);
+  }
+}
+
+function harness(over: Partial<ContextMenusDeps> = {}) {
+  const created: Array<{ id: string; contexts: string[] }> = [];
+  const onClicked = new Event<[{ menuItemId: string | number; linkUrl?: string; srcUrl?: string; pageUrl?: string }, unknown]>();
+  const onCommand = new Event<[string, unknown]>();
+  const menus = {
+    create: (p: { id: string; title: string; contexts: string[] }) => void created.push({ id: p.id, contexts: p.contexts }),
+    removeAll: vi.fn(async () => undefined),
+    onClicked,
+  };
+  const addDownload = vi.fn(async (_spec: DownloadSpec) => ({ taskId: 't' }));
+  const tabs = { query: vi.fn(async () => [{ url: 'https://example.com/watch' }]) };
+  const onError = vi.fn();
+  const deps: ContextMenusDeps = {
+    addDownload: addDownload as unknown as ContextMenusDeps['addDownload'],
+    menus: menus as unknown as ContextMenusDeps['menus'],
+    tabs: tabs as unknown as ContextMenusDeps['tabs'],
+    commands: { onCommand } as unknown as ContextMenusDeps['commands'],
+    onError,
+    ...over,
+  };
+  return { cm: new ContextMenus(deps), created, onClicked, onCommand, addDownload, tabs, onError, menus };
+}
+
+describe('ContextMenus', () => {
+  it('registers a link item and a media item after clearing stale ones', async () => {
+    const { cm, created, menus } = harness();
+    await cm.register();
+    expect(menus.removeAll).toHaveBeenCalled();
+    expect(created).toEqual([
+      { id: LINK_MENU_ID, contexts: ['link'] },
+      { id: MEDIA_MENU_ID, contexts: ['image', 'video', 'audio'] },
+    ]);
+  });
+
+  it('a link click sends linkUrl + pageUrl referrer to download.add', async () => {
+    const { cm, onClicked, addDownload } = harness();
+    await cm.register();
+    onClicked.emit(
+      { menuItemId: LINK_MENU_ID, linkUrl: 'https://cdn.example.com/a.zip', pageUrl: 'https://example.com/p' },
+      undefined,
+    );
+    await Promise.resolve();
+    expect(addDownload).toHaveBeenCalledWith({
+      url: 'https://cdn.example.com/a.zip',
+      referrer: 'https://example.com/p',
+    } satisfies DownloadSpec);
+  });
+
+  it('a media click uses srcUrl', async () => {
+    const { cm, onClicked, addDownload } = harness();
+    await cm.register();
+    onClicked.emit({ menuItemId: MEDIA_MENU_ID, srcUrl: 'https://v.example.com/clip.mp4', pageUrl: 'https://v.example.com' }, undefined);
+    await Promise.resolve();
+    expect(addDownload.mock.calls[0]![0].url).toBe('https://v.example.com/clip.mp4');
+  });
+
+  it('ignores a click on some other extension menu item', async () => {
+    const { cm, onClicked, addDownload } = harness();
+    await cm.register();
+    onClicked.emit({ menuItemId: 'someone-elses-item', linkUrl: 'https://x/a.zip' }, undefined);
+    await Promise.resolve();
+    expect(addDownload).not.toHaveBeenCalled();
+  });
+
+  it('rejects a non-http link with a user-facing error, no download', async () => {
+    const { cm, onClicked, addDownload, onError } = harness();
+    await cm.register();
+    onClicked.emit({ menuItemId: LINK_MENU_ID, linkUrl: 'ftp://legacy/a.zip' }, undefined);
+    await Promise.resolve();
+    expect(addDownload).not.toHaveBeenCalled();
+    expect(onError).toHaveBeenCalledWith(expect.stringMatching(/http/));
+  });
+
+  it('the grab-tab command downloads the active tab URL', async () => {
+    const { cm, onCommand, addDownload, tabs } = harness();
+    await cm.register();
+    onCommand.emit(GRAB_TAB_COMMAND, undefined);
+    await Promise.resolve();
+    await Promise.resolve();
+    expect(tabs.query).toHaveBeenCalled();
+    expect(addDownload.mock.calls[0]![0].url).toBe('https://example.com/watch');
+  });
+
+  it('the grab-tab command prefers the tab handed to the listener', async () => {
+    const { cm, onCommand, addDownload, tabs } = harness();
+    await cm.register();
+    onCommand.emit(GRAB_TAB_COMMAND, { url: 'https://direct.example/page' });
+    await Promise.resolve();
+    expect(tabs.query).not.toHaveBeenCalled();
+    expect(addDownload.mock.calls[0]![0].url).toBe('https://direct.example/page');
+  });
+
+  it('surfaces a download.add failure through onError', async () => {
+    const { cm, onClicked, onError } = harness({
+      addDownload: vi.fn().mockRejectedValue(new Error('daemon down')) as unknown as ContextMenusDeps['addDownload'],
+    });
+    await cm.register();
+    onClicked.emit({ menuItemId: LINK_MENU_ID, linkUrl: 'https://x/a.zip' }, undefined);
+    await Promise.resolve();
+    await Promise.resolve();
+    expect(onError).toHaveBeenCalledWith(expect.stringMatching(/daemon down/));
+  });
+
+  it('dispose() detaches listeners', async () => {
+    const { cm, onClicked, addDownload } = harness();
+    await cm.register();
+    cm.dispose();
+    onClicked.emit({ menuItemId: LINK_MENU_ID, linkUrl: 'https://x/a.zip' }, undefined);
+    await Promise.resolve();
+    expect(addDownload).not.toHaveBeenCalled();
+  });
+});